1. Field of the Invention
This invention relates to a sheet sorting device (hereinafter referred to as the sorter) used for distribution, accumulation, etc. of sheet-like members (hereinafter simply referred to as sheets) carried out from a machine such as a copying machine, a printing machine, a recording machine or other machine (hereinafter referred to as an image forming apparatus) provided with a mechanism for conveying sheet-like members (including various sheet-like members such as copy sheets, printing sheets and recording sheets).
2. Description of the Related Art
The device of this type (the details of which are described in Japanese Patent Application Laid-Open No. 78770/1981) has heretofore been of a construction as shown in FIG. 1 of the accompanying drawings wherein the rear ends 1 of bins 2 are held and only the fore ends of the bins are successively moved upwardly or downwardly by the engagement between engaging members 3 at the fore ends of the bins 2 and a Geneva stop 4 or a spiral cam comprising a single groove. In such a construction, if the angle of inclination of the bins with respect to the direction of sheet conveyance is .alpha., the angle .alpha. differs from bin to bin, and this has led to a disadvantage that the sheet supporting property differs between the bins.
As a method of the eliminating this disadvantage (that is, making the angle of inclination .alpha. of the bins constant), there is a method of vertically moving the bins as a unit and enlarging the spacing between the bins at the sheet carry-out port while successively moving the bins from one side to the other side. For example, as shown in FIG. 2 of the accompanying drawings, the spacing of engaging members 6a, 6b, provided on the bin 6, in the direction of movement (the spacing between 6a-9a and between 6b-9b) is controlled by support frame members 12 and 15, and an engaging member (not shown) provided on the rear end of the bin is also held by the support frame member 12 and therefore, a spiral cam comprising a spiral groove engages the engaging members (e.g. 6a, 6b) at the fore end of the bin, whereby the support frame member 12 itself is moved up and down and thus, the bin group is moved up and down as a unit. In such construction, the aforementioned disadvantage of the non-uniform supporting property of the bins is eliminated, but in the case of a high-speed sorter, when the bin tray group is to be moved upwardly or downwardly, a difficulty is caused when moving the bin tray group of heavy weight intermittently and rapidly, for example, the mechanical abrasion or damage by vibration, noise, shock, etc. Considering, for example, a case where all bins are being moved up in FIG. 2, the engaging members 9a and 9b of the bin 9 support all the load of the bin group, and the load of the bin group shifts to the engaging members 8a and 8b of the bins 8 when the bin 9 moves downwardly. Such shift of all the load takes place intermittently, whereby great noise or vibration occurs and expedites the mechanical abrasion, which in turn shortens the life of the device.
Further, as a method for eliminating such a disadvantage, there is known a method of dividing moving means for the bin group and means for enlarging the spacing between the bins at the sheet carry-out port and making them discrete from each other. For example, as shown in FIG. 3 of the accompanying drawings, a pin 21 for supporting the load of the bin group is provided on a bin frame 20 and this pin 21 is brought into engagement with a lead cam shaft 22 having the shape of a spiral groove to thereby effect continuous upward and downward movement of the bin group as a unit. Also, at the sheet carry-out port, for example, a bin 23, is moved to a position 23, by a spiral cam 24 comprising a groove to thereby enlarge the spacing between the bin 23.sub.1 and 23.sub.2. With such construction, the aforementioned disadvantage of the non-uniform sheet supporting property of the bins and the noise can be eliminated. However, again in this construction, the presence of the lead cam shaft 22 and the engaging pin 21 and the difference in shape between the grooves of the spiral cam 24 and the lead cam shaft cause a phase difference in the direction of height and therefore, a mechanism for alleviating this is necessary and moreover, two large extra lead cam shafts 22 become necessary, thus making the mechanism complicated and bulky, and also there are four locations of engagement with the lead cam shafts, which means a disadvantage that the assemblage and serviceability of the device are remarkably hampered.
Also, in a movable bin type bin shifting device, a chain or wire has been fixed to the ends of a bin unit comprising a plurality of bins and a bin support plate for supporting the bins and the chain or wire has been moved by a discrete driving device to move the bin unit up or down. As another method, a pin fixed to the ends of the bin unit has been operatively associated with a rotatable lead screw and the lead screw has been rotatably controlled to thereby moved the bin unit or down. Thus, in the former example, a brake device for moving the bin unit up or down to a predetermined place and fixing it at the predetermined place has been necessary, and in both of the former and latter examples, as sheets are supported on the bins, the entire bin unit becomes heavier and a driving device of large capacity has become necessary to cover it from first, and this has led to a disadvantage that the increased cost and bulkiness of the device are unavoidable.
Also, in this type of device, as a countermeasure for a case where the movement of the frame is blocked by the extraneous force of an obstruction or the like, a ratchet plate has been provided on a drive motor portion so that the destruction of the machine is avoided with the aid of the idle revolution of the motor, while this has led to complication and increased cost of the mechanism.